Two New Polymethoxylated Flavones, a Class of Compounds with Potential Anticancer Activity, Isolated from Cold Pressed Dancy Tangerine Peel Oil Solids

Abstract

Ten polymethoxylated flavonoids were isolated and characterized from cold pressed tangerine oil solids; they are 5,6,7,3‘,4‘-pentamethoxyflavone (sinensetin) ( I ); 7-hydroxy-3,5,6,3‘,4‘-pentamethoxyflavone ( II ); 5-hydroxy-6,7,8,3‘,4‘-pentamethoxyflavone ( III ); 5,6,7,8,3‘,4‘-hexamethoxyflavone (nobiletin) ( IV ); 5,6,7,8,4‘-pentamethoxyflavone (tangeretin) ( V ); 5,7,8,4‘-tetramethoxyflavone (tetra- O -methylisoscutellarein) ( VI ); 7-hydroxy-3,5,6,8,3‘,4‘-hexamethoxyflavone ( VII ); 5,6,7,4‘-tetramethoxyflavone (tetra- O -methylisoscutellarein) ( VIII ); 3,5,6,7,8,3‘,4‘-heptamethoxyflavone ( IX ); and 5,7,8,3‘,4‘-pentamethoxyflavone ( X ). Structures of the compounds were elucidated on the basis of spectroscopic methods and chemical data. Compounds II and VII are novel natural products; compounds IV, V, and VIII have been reported with significant activity against various strains of carcinoma cells; and compounds I and IV decrease erythrocyte aggregation and sedimentation in vitro . A biological activity screen of other compounds is in progress. Keywords: Polymethoxylated flavones; antitumor activity; Citrus; tangerine oils; Dancy tangerine